1903.] On the Intensely Penetmtin<j Rays of Radium. 



20<> 



The following table gives the relative ionisations, referred to air as 

 unity. The values of the sanies constants for the a and /3 rays formerly 

 found are included, and also measurements of relative ionisation under 

 Rontgen rays. These latter form part of an investigation not 

 hitherto published. 



Relative Ionisations. 



The determinations for the 7 rays are less accurate than the former 

 ones for the a and /? rays, on account of the very much smaller rates of 

 leak which have to be measured. I think, if this be taken into account, 

 there is no reason to doubt that, within the limits of experimental 

 error, the 7 rays give the same values as the ft rays. These values 

 are nearly proportional to the density of the gas, except in the case 

 of hydrogen. The law which holds in the case of Rontgen rays is 

 totally different. 



This conclusion throws some light on the nature of the 7 rays. The 

 view seems to be gaining ground that these are Rontgen rays, produced 

 by the impact of the /3 rays on the radium itself.* This theory seems 



* See, for instance, Madame Curie, * Th^res presentees a laFacultj des Sciences/ 

 1903, p. 83. 



